There is a technique for extracting a plurality of characteristic point candidates from an input image and detecting characteristic points from the extracted characteristic point candidates in order to use the characteristic points for a process to be performed by an information processing device. Japanese Laid-Open Patent Publication No. 2007-233997 discusses that when a pupil is to be detected as a characteristic point from an input image obtained by imaging a person's face, positional relationships between the pupil and other characteristic points such as a mouth corner and a naris are used. For example, in a process using this technique, a plurality of characteristic point candidates that can be characteristic points such as pupils, mouth corners and nares are extracted from an input image obtained by imaging a person's face. In the process, a plurality of combinations of the characteristic point candidates such as the pupils, the mouth corners and the nares are then generated and compared with a model in which positional relationships among characteristic points such as pupils, mouth corners and nares are defined. In the process, as a result of the comparison, characteristic point candidates that are included in a combination that best matches the model are determined as characteristic points such as the pupils, the mouth corners and the nares.
The positions of the pupils that are detected as the characteristic points from the input image are used for the following processes. For example, the positions of the pupils are used for the process in which an information processing device such as a mobile phone or a personal computer tracks movements of the pupils of a user, captures a line of sight of the user, and scrolls a screen displayed on a display or the like on the basis of a movement of the line of sight. In addition, the positions of the pupils are used for the process in which an electronic device that is installed in a vehicle tracks movements of the pupils of a driver, captures a line of sight of the driver, and provides an alarm when the device detects that the driver looks away from a road.